NSW Maritime is investigating a boating incident that occurred off Shellharbour yesterday.

Regional Manager South Coast Craig Whitmore today said the incident happened around 12pm on Sunday as a 4.5m vessel with two adult males and two male children, aged 5 years and 7 years, aboard was returning towards Shellharbour from Bass Point.

When approximately 200m off Bombi Point just south of Shellharbour the vessel was struck on the starboard side by a wave capsizing the vessel.

All four occupants were able to swim to nearby rocks suffering only minor grazes and lacerations.

The vessel washed up on rocks and was unable to be recovered with due to prevailing conditions. Attempts to recover the craft will take place today.

Mr Whitmore said the two children were wearing lifejackets at the time of the incident.

NSW Maritime requires such vessels to carry a lifejacket for each person on board and these must be in good condition, of appropriate size and ready for use at any time. The authority recommends children and poor swimmers wear a lifejacket at all times while in open areas of a boat or at times of heightened risk such as boating offshore.